Miss Chalmers, who won gold for archery in the British Transplant Games, said: “I initially signed up for the marathon in 2011 after seeing my friends complete it.

“I had just come out of hospital and for the first time needed to use oxygen therapy at home, but I was determined that by the following year, I would get myself back on track and healthy enough to run the marathon.

“That didn’t happen as I became completely reliant on oxygen 24/7 and my health deteriorated.

“By May 2012, I was on the list for a life-saving double-lung transplant and in September that year I was lucky enough to receive one.”

She said that after her surgery she knew she no longer had an excuse not to run the marathon and that completing it will be a huge achievement.

“Going from hardly being able to walk up my stairs to being able to run – and a bit of walking – in a marathon is something I’m so glad to have the chance to do,” she said.

Miss Chalmers, from Brighton, said that basic care for cystic fibrosis sufferers to maintain life and keep as healthy as possible was improving, but that many people are not lucky enough to receive a transplant.

She said: “Thanks to the Trust putting money into care and gene therapy research, a major trial of new drugs is now under way.

“This work is only possible through the generosity and support of very kind people, so when it came to picking a charity to run for it was an easy choice.”

Ed Bending, the university’s environmental communications officer, who is running the marathon with his friend, said: “Amanda’s life-saving operation and her amazing recovery are just fantastic and we are all so proud of the resilience she has shown and the can-do attitude that has led her to this point.”

Jennifer Westmoreland, head of the Cystic Fibrosis Trust’s community and fundraising events, said: “Amanda is a brilliant example of what people with cystic fibrosis can achieve when they are given the opportunity. I’m sure her story will inspire others waiting for organ transplants.”